Hello all,

May someone help me to explain in very simple definition, what is the different between QTC (Qualification Test Coupon) and ER (Equivalent Round).
I already read API 6A 21st Edition section 6.4 , but i still didn't get how to distinguish definition both of them.

Maybe to make it simple, i give an example if we want to produce Choke Valve 2", then which one of Choke Valve parts need to be QTC and ER ?

Thanks Before

See More: (ASK) QTC and ER in API 6A 21st Edition